Cadq (.cadq) ransomware virus - removal and decryption options
Written by Tomas Meskauskas on (updated)
What kind of malware is Cadq?
Typically, victims of ransomware attacks cannot access data on their computers or other devices until they pay a ransom. Ransomware is a type of malware that encrypts files stored on a device and generates a ransom note that usually contains details such as an email address to contact the attackers, the price of a decryption tool, etc.
This ransomware belongs to the ransomware family called Djvu. It renames every encrypted file by appending the ".cadq" extension to its filename. For example, it renames "1.jpg" to "1.jpg.cadq", "2.jpg" to "2.jpg.cadq", and so on, and creates the "_readme.txt" file (ransom note). Cadq creates its ransom note in all folders that contain encrypted data.
Screenshot of files encrypted by Cadq (".cadq" extension):
Ransom note overview
As mentioned in the previous paragraph, the ransom note created or displayed by ransomware usually contains contact and payment information (or other details).
The "_readme.txt" ransom note is created to inform victims that all their documents, images, databases, and other files are encrypted using strong cryptography, and the only way to regain access to them is to decrypt them with a specific decryption software and unique key.
The price of these decryption tools depends on how fast victims would write an email to helpteam@mail.ch, helpmanager@airmail.cc. More precisely, the attackers charge $980 for file recovery and offer a 50% discount for victims who would make the payment within 72 hours after the attack.
Although, it is not recommended to pay a ransom to any ransomware developers, as there is no guarantee that victims will get their data back (will receive a decryption tool or tools), even if they fully comply with the requirements of the attackers.
More about ransomware
Typically, victims cannot regain access to the encrypted files without having to use a specific decryption tool (software or key) that can be provided only by the attackers. Unfortunately, there are no third-party tools freely available on the Internet that could be capable of decrypting Cadq's encryption.
In such cases, there is only one way to recover files: to restore them from a backup made before the ransomware attack. In order to avoid losing more files than the installed ransomware has already encrypted (to prevent ransomware from encrypting new files), it is required to uninstall it from the operating system.
It is worthwhile to mention that removal of ransomware does not make encrypted files accessible. They remain encrypted even if ransomware that has encrypted them is no longer installed.
To summarize, victims of a ransomware attack cannot access, use their files, and are provided with instructions on how to contact the attackers, pay them a ransom, or other details.
Differences between ransomware attacks
Usually, the only main difference between ransomware attacks is the amount of cryptocurrency (typically, Bitcoin) the attackers ask to pay them for the decryption tools and cryptographic algorithm that is used to encrypt files.
Sometimes it is possible to decrypt files without paying for any tools, but only when the installed ransomware has some vulnerabilities, and there is some free decryption tool available for download on the Internet.
However, it is not very common. For this reason, it is recommended to create data backups regularly and keep them on a remote served, for example, Cloud or unplugged storage device. More ransomware examples are LOTUS, Word and Ygkz.
How did ransomware infect my computer?
Usually, ransomware and other malicious software spreads through emails (malspam campaigns), questionable sources for downloading files, programs, fake software updating tools, Trojans, and unofficial software activation tools ('cracking' tools).
Users install ransomware or other malware via emails when they open a malicious attachment or a file that they have downloaded via a website link in the received malspam email.
Typically, such emails are used to trick recipients into opening malicious Microsoft Office documents, ZIP, RAR or other archive files, PDF documents, executable files (like.exe), or JavaScript files. It is important to mention that cybercriminals behind malspam campaigns pretend to be legitimate companies, organizations. They disguise their emails as important, official.
Files that users download via unreliable sources can be the reason behind the installation of malware too. It is common that malware authors disguise malicious files as regular and wait for someone to download and open them. Such files infect systems after being opened.
Examples of unreliable sources for downloading files, programs are Peer-to-Peer networks (e.g., torrent clients), free file hosting pages, freeware download pages, unofficial websites. Fake software updating tools infect computers by installing malware instead of updating, fixing some already installed software, or by exploiting bugs, flaws of installed software that is out of date.
A trojan is a type of malware that can be designed to install other software of this kind. Usually, malware of this type is disguised as legitimate software. Once installed, a Trojan can start causing chain infections. Software 'cracking' tools are illegal tools that activate licensed software.
However, cybercriminals often inject malicious code into such tools to distribute malware.
| Name | Cadq virus |
| Threat Type | Ransomware, Crypto Virus, Files locker |
| Encrypted Files Extension | .cadq |
| Ransom Demanding Message | _readme.txt |
| Free Decryptor Available? | Partial (more information below). |
| Ransom Amount | $980/$490 |
| Cyber Criminal Contact | helpteam@mail.ch, helpmanager@airmail.cc |
| Detection Names | Avast (Win32:RansomX-gen [Ransom]), BitDefender (Trojan.GenericKDZ.73052), ESET-NOD32 (A Variant Of Win32/Kryptik.HJMU), Kaspersky (HEUR:Exploit.Win32.Shellcode.gen), Microsoft (Trojan:Win32/Glupteba!ml), Full List Of Detections (VirusTotal) |
| Symptoms | Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files. |
| Additional Information | This malware is designed to show a fake Windows Update window and modify the Windows "hosts" file to prevent users from accessing cyber security websites (more information below). |
| Distribution methods | Infected email attachments (macros), torrent websites, malicious ads. |
| Damage | All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection. |
| Malware Removal (Windows) | To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner. |
How to protect yourself from ransomware infections?
Avoid opening downloads from questionable websites, various Peer-to-Peer networks, third party downloaders, free file hosting page, and so on: download files, software only from official, trustworthy websites and via direct links. Do not open email attachments or links in emails that are not relevant, sent from unknown, suspicious addresses.
Make sure to keep the installed operating system and software up to date. Update or activate the installed software with implemented functions or tools that its official developers provide. Never ever use any unofficial, third-party tools neither to update or activate any software.
Very often, such tools are used to distribute malware. Also, software 'cracking' is considered an illegal activity. And lastly, scan the operating system for viruses and other threats regularly, and do it with a reputable antivirus or ant-spyware suite.
If your computer is already infected with Cadq, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.
Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data ("_readme.txt"):
Text presented in Cadq ransomware's text file ("_readme.txt"):
ATTENTION!
Don't worry, you can return all your files!
All your files like pictures, databases, documents and other important are encrypted with strongest encryption and unique key.
The only method of recovering files is to purchase decrypt tool and unique key for you.
This software will decrypt all your encrypted files.
What guarantees you have?
You can send one of your encrypted file from your PC and we decrypt it for free.
But we can decrypt only 1 file for free. File must not contain valuable information.
You can get and look video overview decrypt tool:
hxxps://we.tl/t-9tWwjPzDLY
Price of private key and decrypt software is $980.
Discount 50% available if you contact us first 72 hours, that's price for you is $490.
Please note that you'll never restore your data without payment.
Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours.
To get this software you need write on our e-mail:
helpteam@mail.chReserve e-mail address to contact us:
helpmanager@airmail.ccYour personal ID:
-
Screenshot of fake Windows update pop-up displayed during the encryption:
IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also add a number of entries to the Windows "hosts" file. The entries contain URLs of various websites, most of which are related to malware removal.
This is done to prevent users from accessing malware security websites and seeking help. Our website (PCrisk.com) is also on the list.
Removing these entries, however, is simple - you can find detailed instructions in this article (note that, although the steps are shown in the Windows 10 environment, the process is virtually identical on all versions of the Microsoft Windows operating system).
Screenshot of websites added to Windows hosts file:
There are currently two versions of Djvu ransomware infections: old and new. The old versions were designed to encrypt data by using a hard-coded "offline key" whenever the infected machine had no internet connection or the server was timing out/not responding.
Therefore, some victims were able to decrypt data using a tool developed by cyber security researcher, Michael Gillespie, however, since the encryption mechanism has been slightly changed (hence the new version, released in August, 2019), the decrypter no longer works and it is not supported anymore.
If your data has been encrypted by an older version, you might be able to restore it with the another tool developed by Emsisoft and Michael Gillespie. It supports a total of 148 Djvu's variants and you can find more information, as well as download link and decryption instructions in Emsisoft's official page.
Screenshot of Djvu decryption tool by Emsisoft and Michael Gillespie:
Additionally, Emsisoft is now providing a service that allows to decrypt data (again, only if it was encrypted by Djvu variants released before August, 2019) for those victims who have a pair of the same file before and after the encryption.
All victims have to do is upload a pair of original and encrypted file to Emsisoft's Djvu decryption page and download the aforementioned decryption tool (the download link will be provided after uploading files). Note that the file processing may take some time so be patient.
It is also worth mentioning that the system must have an Internet connection during the entire decryption process, otherwise it will fail.
Screenshot of Emsisoft's Djvu decryption service page:
Some victims state that they've successfully restored a part of encrypted data using PhotoRec tool developed by CGSecurity (Christophe Grenier). You can download this tool from CGSecurity's official website.
Screenshot of PhotoRec application:
Now it is worth noting that Djvu ransomware does not encrypt the entire file. Instead, it encrypts only a portion (start) of the file, thereby making it unusable. Luckily, in some cases it is possible to restore other part of the file, which is not encrypted.
This is useful when it comes to audio/video files, because even though the start won't be restored, you'll still be able to use most of it. To restore audio/video data we advise you to use Media_Repair tool developed by DiskTuna. This tool is extremely simple and completely free. You can find the user manual as well as download the tool directly from DiskTuna's website.
Screenshot of Media_Repair application developed by DiskTuna:
Cadq ransomware removal:
Instant automatic malware removal:
Manual threat removal might be a lengthy and complicated process that requires advanced IT skills. Combo Cleaner is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
▼ DOWNLOAD Combo Cleaner
By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. To use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by Rcs Lt, the parent company of PCRisk.com read more.
Video suggesting what steps should be taken in case of a ransomware infection:
Quick menu:
- What is Cadq virus?
- STEP 1. Reporting ransomware to authorities.
- STEP 2. Isolating the infected device.
- STEP 3. Identifying the ransomware infection.
- STEP 4. Searching for ransomware decryption tools.
- STEP 5. Restoring files with data recovery tools.
- STEP 6. Creating data backups.
If you are a victim of a ransomware attack we recommend reporting this incident to authorities. By providing information to law enforcement agencies you will help track cybercrime and potentially assist in the prosecution of the attackers. Here's a list of authorities where you should report a ransomware attack. For the complete list of local cybersecurity centers and information on why you should report ransomware attacks, read this article.
List of local authorities where ransomware attacks should be reported (choose one depending on your residence address):
USA - Internet Crime Complaint Centre IC3
United Kingdom - Action Fraud
Spain - Policía Nacional
France - Ministère de l'Intérieur
Germany - Polizei
Italy - Polizia di Stato
The Netherlands - Politie
Poland - Policja
Portugal - Polícia Judiciária
Isolating the infected device:
Some ransomware-type infections are designed to encrypt files within external storage devices, infect them, and even spread throughout the entire local network. For this reason, it is very important to isolate the infected device (computer) as soon as possible.
Step 1: Disconnect from the internet.
The easiest way to disconnect a computer from the internet is to unplug the Ethernet cable from the motherboard, however, some devices are connected via a wireless network and for some users (especially those who are not particularly tech-savvy), disconnecting cables may seem troublesome. Therefore, you can also disconnect the system manually via Control Panel:
Navigate to the "Control Panel", click the search bar in the upper-right corner of the screen, enter "Network and Sharing Center" and select search result: 
Click the "Change adapter settings" option in the upper-left corner of the window: 
Right-click on each connection point and select "Disable". Once disabled, the system will no longer be connected to the internet. To re-enable the connection points, simply right-click again and select "Enable". 
Step 2: Unplug all storage devices.
As mentioned above, ransomware might encrypt data and infiltrate all storage devices that are connected to the computer. For this reason, all external storage devices (flash drives, portable hard drives, etc.) should be disconnected immediately, however, we strongly advise you to eject each device before disconnecting to prevent data corruption:
Navigate to "My Computer", right-click on each connected device, and select "Eject": 
Step 3: Log-out of cloud storage accounts.
Some ransomware-type might be able to hijack software that handles data stored within "the Cloud". Therefore, the data could be corrupted/encrypted. For this reason, you should log-out of all cloud storage accounts within browsers and other related software. You should also consider temporarily uninstalling the cloud-management software until the infection is completely removed.
Identify the ransomware infection:
To properly handle an infection, one must first identify it. Some ransomware infections use ransom-demand messages as an introduction (see the WALDO ransomware text file below).
This, however, is rare. In most cases, ransomware infections deliver more direct messages simply stating that data is encrypted and that victims must pay some sort of ransom. Note that ransomware-type infections typically generate messages with different file names (for example, "_readme.txt", "READ-ME.txt", "DECRYPTION_INSTRUCTIONS.txt", "DECRYPT_FILES.html", etc.). Therefore, using the name of a ransom message may seem like a good way to identify the infection. The problem is that most of these names are generic and some infections use the same names, even though the delivered messages are different and the infections themselves are unrelated. Therefore, using the message filename alone can be ineffective and even lead to permanent data loss (for example, by attempting to decrypt data using tools designed for different ransomware infections, users are likely to end up permanently damaging files and decryption will no longer be possible even with the correct tool).
Another way to identify a ransomware infection is to check the file extension, which is appended to each encrypted file. Ransomware infections are often named by the extensions they append (see files encrypted by Qewe ransomware below).
This method is only effective, however, when the appended extension is unique - many ransomware infections append a generic extension (for example, ".encrypted", ".enc", ".crypted", ".locked", etc.). In these cases, identifying ransomware by its appended extension becomes impossible.
One of the easiest and quickest ways to identify a ransomware infection is to use the ID Ransomware website. This service supports most existing ransomware infections. Victims simply upload a ransom message and/or one encrypted file (we advise you to upload both if possible).
The ransomware will be identified within seconds and you will be provided with various details, such as the name of the malware family to which the infection belongs, whether it is decryptable, and so on.
Example 1 (Qewe [Stop/Djvu] ransomware):
Example 2 (.iso [Phobos] ransomware):
If your data happens to be encrypted by ransomware that is not supported by ID Ransomware, you can always try searching the internet by using certain keywords (for example, a ransom message title, file extension, provided contact emails, crypto wallet addresses, etc.).
Search for ransomware decryption tools:
Encryption algorithms used by most ransomware-type infections are extremely sophisticated and, if the encryption is performed properly, only the developer is capable of restoring data. This is because decryption requires a specific key, which is generated during the encryption. Restoring data without the key is impossible. In most cases, cybercriminals store keys on a remote server, rather than using the infected machine as a host. Dharma (CrySis), Phobos, and other families of high-end ransomware infections are virtually flawless, and thus restoring data encrypted without the developers' involvement is simply impossible. Despite this, there are dozens of ransomware-type infections that are poorly developed and contain a number of flaws (for example, the use of identical encryption/decryption keys for each victim, keys stored locally, etc.). Therefore, always check for available decryption tools for any ransomware that infiltrates your computer.
Finding the correct decryption tool on the internet can be very frustrating. For this reason, we recommend that you use the No More Ransom Project and this is where identifying the ransomware infection is useful. The No More Ransom Project website contains a "Decryption Tools" section with a search bar. Enter the name of the identified ransomware, and all available decryptors (if there are any) will be listed.
Restore files with data recovery tools:
Depending on the situation (quality of ransomware infection, type of encryption algorithm used, etc.), restoring data with certain third-party tools might be possible. Therefore, we advise you to use the Recuva tool developed by CCleaner. This tool supports over a thousand data types (graphics, video, audio, documents, etc.) and it is very intuitive (little knowledge is necessary to recover data). In addition, the recovery feature is completely free.
Step 1: Perform a scan.
Run the Recuva application and follow the wizard. You will be prompted with several windows allowing you to choose what file types to look for, which locations should be scanned, etc. All you need to do is select the options you're looking for and start the scan. We advise you to enable the "Deep Scan" before starting, otherwise, the application's scanning capabilities will be restricted.
Wait for Recuva to complete the scan. The scanning duration depends on the volume of files (both in quantity and size) that you are scanning (for example, several hundred gigabytes could take over an hour to scan). Therefore, be patient during the scanning process. We also advise against modifying or deleting existing files, since this might interfere with the scan. If you add additional data (for example, downloading files/content) while scanning, this will prolong the process:
Step 2: Recover data.
Once the process is complete, select the folders/files you wish to restore and simply click "Recover". Note that some free space on your storage drive is necessary to restore data:
Create data backups:
Proper file management and creating backups is essential for data security. Therefore, always be very careful and think ahead.
Partition management: We recommend that you store your data in multiple partitions and avoid storing important files within the partition that contains the entire operating system. If you fall into a situation whereby you cannot boot the system and are forced to format the disk on which the operating system is installed (in most cases, this is where malware infections hide), you will lose all data stored within that drive. This is the advantage of having multiple partitions: if you have the entire storage device assigned to a single partition, you will be forced to delete everything, however, creating multiple partitions and allocating the data properly allows you to prevent such problems. You can easily format a single partition without affecting the others - therefore, one will be cleaned and the others will remain untouched, and your data will be saved. Managing partitions is quite simple and you can find all the necessary information on Microsoft's documentation web page.
Data backups: One of the most reliable backup methods is to use an external storage device and keep it unplugged. Copy your data to an external hard drive, flash (thumb) drive, SSD, HDD, or any other storage device, unplug it and store it in a dry place away from the sun and extreme temperatures. This method is, however, quite inefficient, since data backups and updates need to be made regularly. You can also use a cloud service or remote server. Here, an internet connection is required and there is always the chance of a security breach, although it's a really rare occasion.
We recommend using Microsoft OneDrive for backing up your files. OneDrive lets you store your personal files and data in the cloud, sync files across computers and mobile devices, allowing you to access and edit your files from all of your Windows devices. OneDrive lets you save, share and preview files, access download history, move, delete, and rename files, as well as create new folders, and much more.
You can back up your most important folders and files on your PC (your Desktop, Documents, and Pictures folders). Some of OneDrive’s more notable features include file versioning, which keeps older versions of files for up to 30 days. OneDrive features a recycling bin in which all of your deleted files are stored for a limited time. Deleted files are not counted as part of the user’s allocation.
The service is built using HTML5 technologies and allows you to upload files up to 300 MB via drag and drop into the web browser or up to 10 GB via the OneDrive desktop application. With OneDrive, you can download entire folders as a single ZIP file with up to 10,000 files, although it can’t exceed 15 GB per single download.
OneDrive comes with 5 GB of free storage out of the box, with an additional 100 GB, 1 TB, and 6 TB storage options available for a subscription-based fee. You can get one of these storage plans by either purchasing additional storage separately or with Office 365 subscription.
Creating a data backup:
The backup process is the same for all file types and folders. Here’s how you can back up your files using Microsoft OneDrive
Step 1: Choose the files/folders you want to backup.
Click the OneDrive cloud icon to open the OneDrive menu. While in this menu, you can customize your file backup settings.
Click Help & Settings and then select Settings from the drop-down menu.
Go to the Backup tab and click Manage backup.
In this menu, you can choose to backup the Desktop and all of the files on it, and Documents and Pictures folders, again, with all of the files in them. Click Start backup.
Now, when you add a file or folder in the Desktop and Documents and Pictures folders, they will be automatically backed up on OneDrive.
To add folders and files, not in the locations shown above, you have to add them manually.
Open File Explorer and navigate to the location of the folder/file you want to backup. Select the item, right-click it, and click Copy.
Then, navigate to OneDrive, right-click anywhere in the window and click Paste. Alternatively, you can just drag and drop a file into OneDrive. OneDrive will automatically create a backup of the folder/file.
All of the files added to the OneDrive folder are backed up in the cloud automatically. The green circle with the checkmark in it indicates that the file is available both locally and on OneDrive and that the file version is the same on both. The blue cloud icon indicates that the file has not been synced and is available only on OneDrive. The sync icon indicates that the file is currently syncing.
To access files only located on OneDrive online, go to the Help & Settings drop-down menu and select View online.
Step 2: Restore corrupted files.
OneDrive makes sure that the files stay in sync, so the version of the file on the computer is the same version on the cloud. However, if ransomware has encrypted your files, you can take advantage of OneDrive’s Version history feature that will allow you to restore the file versions prior to encryption.
Microsoft 365 has a ransomware detection feature that notifies you when your OneDrive files have been attacked and guide you through the process of restoring your files. It must be noted, however, that if you don’t have a paid Microsoft 365 subscription, you only get one detection and file recovery for free.
If your OneDrive files get deleted, corrupted, or infected by malware, you can restore your entire OneDrive to a previous state. Here’s how you can restore your entire OneDrive:
1. If you're signed in with a personal account, click the Settings cog at the top of the page. Then, click Options and select Restore your OneDrive.
If you're signed in with a work or school account, click the Settings cog at the top of the page. Then, click Restore your OneDrive.
2. On the Restore your OneDrive page, select a date from the drop-down list. Note that if you're restoring your files after automatic ransomware detection, a restore date will be selected for you.
3. After configuring all of the file restoration options, click Restore to undo all the activities you selected.
The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups.
Frequently Asked Questions (FAQ)
How was my computer hacked and how did hackers encrypt my files?
Cybercriminals have been observed using email, websites hosting cracked software or cracking tools, and pages offering to download videos from YouTube to distribute Djvu ransomware. In other cases, they use P2P networks, third-party downloaders, free file hosting websites (and other unreliable sources for downloading software or files), Trojans, and fake software updating tools.
How to open ".cadq" files?
These files are encrypted by the Cadq ransomware. Thus, they cannot be opened.
How can I decrypt ".cadq" files for free?
Most Djvu ransomware variants encrypt files using an online key. It means that files cannot be decrypted without tools that usually only the attackers have. It is possible to decrypt files without the interference of the attackers when they are encrypted using an offline key. It may be possible to do that with Emsisoft's Djvu decryption software (more information above).
Should I pay a ransom?
It is not recommended to pay cybercriminals for data decryption because they may not provide a decryption tool. Also, paying them may encourage them to continue ransomware attacks.
Will Combo Cleaner help me remove Cadq ransomware?
Yes, Combo Cleaner will eliminate ransomware from an infected computer. Using antivirus software to remove ransomware prevents more data loss. However, files remain encrypted. Antivirus software cannot decrypt files.
Outstanding!
▼ Show Discussion